For everyone's enjoyment, here is a technical summary of some of LEDs advantages, a few of which we've been talking about:1. Direct control of the light source1a. "No Color Wheel:"
The color wheel currently absorbs a significant amount of light to enable the system to be controlled. It presents an inefficiency that LEDs will not have to overcome1b. "No more rainbows:"
Since the colors can be cycled extremely quickly, much quicker than mechanical systems, the rainbow problem should no longer be observable by anyone.
Additional information on this topic can be found below as Appendix A1c "No fixed color order, duration, or intensity"
Currently, the DMD / DLP system works by having a constant know light source and modulating a mirror to adjust the intensity of each pixel. The video processor must work with a fixed color sequence, with each color having a fixed duration of type to create the image. Put directly, the system must make use of 100% Red for 2.5mS then 100% Green for 2.5mS then 100% Blue for 2.5mS.
An LED system does not contain this limit. The video processor can control the light based on the properties of the image it is attempting to display. It can control the color, the brightness, and the duration of any color the LED array can produce. Again, put directly, the processor could order up 90% Red for 1mS then 100% Blue for 2.0mS then 20% Green for 0.5mS then 50% Green AND
50% Red (a dim yellow) for 1.0mS then 100% Red and
100% Green and
100% Blue (pure white) for 1.8mS.... I hope everyone can see what I am getting at.2. LEDs simplify cooling.2a. "No IR / UV component of light"
Current lamps produce more than just visible light, they produce infrared and ultraviolet. These must be filtered and also create a significant amount of heat which propagates through the optical system. An LED system lacks this concern and should create less cooling demand for the optics (quieter fans).2b. "Thermal energy can be cooled directly."
LEDs can have heatsinks attached to them directly to aid in the cooling of the devices without interfering with their light output. This should enable more efficient cooling (quieter fans).3. Service life between 10,000 and 100,000 hours.
With an extended service life, you would never have to replace a bulb. A MTBF (Mean time before failure) of 10,000 hours is considered the benchmark for consumer electronics; for a tv thats watching 4 hours a day, everyday
for over 6 years.4. LEDs are more robust than existing bulbs.
LEDs can withstand far greater mechanical shocks than bulbs can and should mean a sturdier mobile projector.5. Arc bulbs require a complex power control system
to prevent the color of the light from changing. The power control system for LEDs is simplier.6. Instant on
LEDs do not need to warm-up and stabilize as arc-bulbs do and projectors using LEDs would turn on as fast as direct view LCDs.
Enjoy!Appendix A: Continued 1b information
Note, the following is a fairly technical list of articles/quotes and I apologize that it is not intriniscially obvious why this proves LEDs can elliminate rainbows.
From this article
, the following quote is used:
According to a talk I had with Gene O'Donnell, Director of Advanced Displays and Systems at Thomson (RCA), he said an Air Force study of DLP color breakup determined that 2500 sub-frames per second would be required in a sequential color display single-chip DLP system in order to totally avoid color breakup effects.
This equates to a subframe lasting for 400uS. Also please note that a subframe is not a complete image, but the longest time that one color is displayed before switching to a new color.
From this DLP White paper
In this phased reset mode the minimum LSB period is determined by the mirror transition and settle time (about 18us...) plus the time required to reload the mirror section with new data (about 6us).
That gives a switching window of 24uS. This is significantly faster than our mimimum subframe duration.
Although I won't site any sources (I leave it up to the critic to disprove) LEDs can switch in less than 0.1uS, but even at 10uS they still more than fast enough.
[Edit: Added 1b Info]